Material Cuts Delays in Contact Lens Container Production

The Challenge

A leading North American medical contact manufacturer faced a challenge when molding the gasket for a contact lens container.

The two-gram gasket is a critical component for keeping contact lens solution from leaking out of the container. The manufacturer produces 7.5 million cases per year, and used liquid injection molded (LIM) silicone to mold this component. However, the silicone was sticking to the mold and inner workings of the molding machine. This not only caused a high scrap rate, but also led to frequent interruptions in the automated process so that the mold and machine could be cleaned.

Because low durometer (softer) material is a requirement for this application, the manufacturer considered a switch to a thermoplastic elastomer (TPE). The company tried several TPE grades, hoping to find a material that would eliminate the adhesion problem while providing comparable softness to silicone. But even if it could find the right TPE, the company was concerned about the additional cost of new tooling, and wanted to achieve a rapid return on its investment.

The Solution

The manufacturer worked with PolyOne to formulate a custom Versaflex™ TPE that featured a low durometer with excellent resistance to adhesion (sticking). Testing showed that this TPE would not stick to the machinery or itself.

But before making the decision to switch from silicone to the Versaflex material, the company needed to feel confident that it would recoup its capital, which included a $50,000 investment in new tooling, within 12 months.

PolyOne helped the customer calculate costs for the 12-month period. In addition to a lower material cost than silicone, the custom TPE offered cycle time efficiencies, lower part weight due to its lower specific gravity, and reduced scrap rates. Projections showed the cost of a new tool would be recouped within months, enabling the manufacturer to move forward with confidence.

The Impact

Armed with a new specialty TPE solution, the medical manufacturer handled gasket adhesion with a material that outperformed that not only silicone, but also conventional TPEs. On top of that, the manufacturer had the evidence of projected savings and ROI to confidently invest in new tooling.

With the new material, the manufacturer is expected to save $122,000 per year vs. silicone. Even after the cost of the new tooling, the company will save about $72,000 the first year, an impressive and rapid return on the investment in new tooling.